Process for drilling at least two holes in a two-step cycle

ABSTRACT

A process is provided for drilling at least two holes with a device. The device has at least one double-spindle machining unit ( 2 ), which can be moved along a first travel axis (Y), and a linear carriage unit ( 3 ) with a duplicate work holding fixture ( 4 ) for two workpieces ( 5.1, 5.2 ). The linear carriage unit can be moved along a second travel axis (X) independently from the machining unit. The following steps are performed one after another: 
     Drilling of a first hole in a first workpiece ( 5.1 ) (first cycle), 
     subsequent drilling of a second hole in the first workpiece ( 5.1 ) and simultaneous drilling of a first hole in a second workpiece ( 5.2 ) (second cycle), 
     removal of the first workpiece ( 5.1 ), 
     loading of a third workpiece ( 5.3 ), and 
     drilling of a second hole in the second workpiece ( 5.2 ) and simultaneous drilling of a first hole in the third workpiece ( 5.3 ).

FIELD OF THE INVENTION

The present invention pertains to a process for drilling at least twoholes in a workpiece in a two-step cycle by means of at least onedouble-spindle machining unit.

BACKGROUND OF THE INVENTION

Two machining variants of simultaneously drilling two holes in aworkpiece have been known in practice. They are:

Variant 1: Drilling with the use of double-spindle machining centers, or

Variant 2: Drilling on two-way drills.

In Variant 1, two holes are drilled simultaneously in a workpiece ineach cycle. The distance between the centers of the two holes is equalto the distance between the axes of the tool spindles. However, thedistance between the axes of the tool spindles is not variable,especially in machine tools of a simple design. However, this means thatdifferent workpieces with different distances between the centers of theholes would have to be machined on different machine tools, which wouldlead to high investment cost for a comparatively slight change. Analternative could be at best the use of new bearings for the toolspindles, and these bearings would be weaker in the case of a smallerdistance between the holes in the workpiece. However, the effortnecessary for this is rather high and also undesirable, because aweakening of the tool spindle bearing as a whole is disadvantageous. Theflexibility of the machining possibilities is thus very greatly limitedin the case of the machining of workpieces with double-spindle machiningcenters.

In Variant 2, two workpieces are machined simultaneously by twomachining units acting usually in opposite directions due to themovement of a duplicate work holding fixture in two-step cycle. Eventhough the flexibility of this technological process is substantiallyhigher than that of the above-described Variant 1, two finishedworkpieces are present here after each cycle of the machine, and theseworkpieces must be removed and reloaded simultaneously. This requires ahigh level of technical effort for the upstream and downstream unitsand/or machining stations.

SUMMARY AND OBJECTS OF THE INVENTION

The basic technical problem of the present invention is to change thetechnological process of drilling at least two holes in a workpiece suchthat while the flexibility and the output of the machine are high,simpler peripheral means can be used.

A device for carrying out the process according to the present inventionhas, to begin with, at least one double-spindle machining unit, which issimultaneously movable along a first travel axis, and a linear carriageunit with a duplicate work holding fixture for two workpieces, which canbe moved along a second travel axis independently from the machiningunit. The technical problem is accomplished according to the presentinvention by first drilling a first hole in a first workpiece in a firstcycle, after which a second hole is drilled in the first workpiece and afirst hole is simultaneously drilled in a second workpiece in a secondcycle.

Once this second cycle has been concluded as well, the first workpieceis removed from the duplicate work holding fixture and the duplicatework holding fixture is loaded with another workpiece. A second hole isnow drilled in the second workpiece and a first hole is drilled in theworkpiece loaded last. The workpieces are machined one after another,and a completely machined workpiece is removed after each work cyclebeginning from the second cycle, and the duplicate work holding fixtureis loaded with a new workpiece (blank).

Such a process offers the advantages of a higher flexibility along witha simultaneous simplification of the design of the peripheral means asthey are usually used in double-spindle machining centers, correspondingto the above-described prior-art Variant 1.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its uses,reference is made to the accompanying drawings and descriptive matter inwhich a preferred embodiment of the invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view showing a horizontal drill with a linearcarriage unit.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the drawings in particular, the process according to thepresent invention will be described below on the basis of the specialmachining of a ball piece on a horizontal drill. Such a ball piece has acentral ball body with two pins arranged diametrically opposed, in whicha hole each is to be drilled. The horizontal drill shown in FIG. 1comprises a substructure 1 with two double-spindle machining units 2,which are movable simultaneously along a travel axis Y, and a linearcarriage unit 3 with a duplicate work holding fixture 4 for twoworkpieces, which are movable along a travel axis X. In the embodimentshown, the travel axes X and Y extend approximately at right angles toone another.

At the beginning of the machining, the duplicate work holding fixture 4is first loaded with a first workpiece such as workpiece 5.1. After thetravel of the machining units 2 along the travel axis Y toward theworkpiece, the first hole (No. 1) is now drilled in the first workpiece5.1.

Once this hole (No. 1) has been finished, the first workpiece 5.1 ismoved along the travel axis X by means of the linear carriage unit 3 bya certain amount, which is equal to the distance between the centers ofthe holes of a workpiece.

The duplicate work holding fixture 4 is subsequently loaded with thesecond workpiece 5.2. The second hole is drilled in the first workpieceand the first hole is drilled in the second workpiece simultaneously dueto the subsequent feed motion of the machining unit 2.

The first workpiece 5.1 can now be removed and a new workpiece blank 5.3can be inserted into the duplicate work holding fixture. After movingthe workpieces together with the duplicate work holding fixture 4 intothe starting position, the first hole is drilled in the third workpiecetogether with the second hole in the second workpiece.

Once both holes have been finished in the second workpiece (5.2), thisworkpiece is also removed from the duplicate work holding fixture 4 andanother workpiece is loaded.

The duplicate work holding fixture 4 is correspondingly moved along thetravel axis X after each operation by an amount that is equal to thedistance between the centers of the holes in the workpieces.

The process according to the present invention creates a continuousloading and unloading process involving one workpiece each time, eventhough two workpieces are machined simultaneously. With high flexibilityand high output of the machine, simpler peripheral means can thus beused for loading and unloading the workpieces.

While a specific embodiment of the invention has been shown anddescribed in detail to illustrate the application of the principles ofthe invention, it will be understood that the invention may be embodiedotherwise without departing from such principles.

What is claimed is:
 1. A process for drilling at least two holes in eachof several workpieces, the process comprising the steps of providing: adevice, which has at least one double-spindle machining unit, which canbe moved along a first travel axis, and a linear carriage unit with aduplicate work holding fixture for two of the workpieces, wherein thelinear carriage unit can be moved along a second travel axisindependently from the machining unit; drilling a first hole in a firstworkpiece; subsequent to said step of drilling a first hole, drilling asecond hole in the first workpiece and simultaneously drilling a firsthole in a second workpiece; removing the first workpiece from theduplicate work holding fixture; loading a third workpiece onto theduplicate work holding fixture; and drilling a second hole in the secondworkpiece and simultaneous drilling a first hole in the third workpiece.2. A process in accordance with claim 1, wherein each step of drillingforms a cycle and a finished workpiece is removed after each cyclefollowing a second cycle and the duplicate work holding fixture isloaded with another workpiece.
 3. A process in accordance with claim 1,wherein a distance between the holes in the workpiece is determined bythe amount of the travel of the double-spindle machining unit.
 4. Aprocess in accordance with claim 2, wherein a distance between the holesin the workpiece is determined by the amount of the travel of thedouble-spindle machining unit.
 5. A process for drilling at least twoholes in each of several workpieces, the process comprising the stepsof: providing a device, which has at least one double-spindle machiningunit, which can be moved along a first travel axis, and a linearcarriage unit with a duplicate work holding fixture for two of theworkpieces, wherein the linear carriage unit can be moved along a secondtravel axis independently from the machining unit; loading a firstworkpiece onto the duplicate work holding fixture and loading a secondworkpiece onto the duplicate work holding fixture; drilling a first holein the first workpiece in a first cycle; in a second cycle drilling asecond hole in the first workpiece and simultaneously drilling a firsthole in a second workpiece; removing the first workpiece from theduplicate work holding fixture; loading a third workpiece onto theduplicate work holding fixture; and in a third cycle drilling a secondhole in the second workpiece and simultaneous drilling a first hole inthe third workpiece.
 6. A process in accordance with claim 5, wherein afinished workpiece is removed after each cycle following the secondcycle and the duplicate work holding fixture is loaded with anotherworkpiece.
 7. A process in accordance with claim 5, wherein a distancebetween the holes in the workpiece is determined by the amount of thetravel of the double-spindle machining unit.
 8. A process in accordancewith claim 6, wherein a distance between the holes in the workpiece isdetermined by the amount of the travel of the double-spindle machiningunit.
 9. A process for drilling at least two holes in each of severalworkpieces with a device, which has at least one double-spindlemachining unit, which can be moved along a first travel axis, and alinear carriage unit with a duplicate work holding fixture for two ofthe workpieces, wherein the linear carriage unit can be moved along asecond travel axis independently from the machining unit, the processcomprising the steps of: drilling a first hole in a first workpieceduring a first drilling phase; subsequent to said first drilling phase,drilling a second hole in the first workpiece and simultaneouslydrilling a first hole in a second workpiece; removing the firstworkpiece from the duplicate work holding fixture; loading a thirdworkpiece onto the duplicate work holding fixture; and drilling a secondhole in the second workpiece and simultaneous drilling a first hole inthe third workpiece during a third drilling phase.
 10. A process inaccordance with claim 9, a finished workpiece is removed after eachdrilling phase following the second drilling phase and the duplicatework holding fixture is loaded with another workpiece.
 11. A process inaccordance with claim 9, wherein a distance between the holes in theworkpiece is determined by the amount of the travel of thedouble-spindle machining unit.
 12. A process in accordance with claim10, wherein a distance between the holes in the workpiece is determinedby the amount of the travel of the double-spindle machining unit.